The need for improved food preservation methods is great. It has been estimated that about one quarter of the world's food supply is lost as a result of microbial spoilage and food-borne microbial infections represent a constant and serious threat to human health.
Fungal spoilage can lead to serious economic losses. Several food products e.g. agricultural products, dairy and meat products, fruits and vegetables and derived products, bakery products and cosmetics are very susceptible to fungal growth. Examples of dairy products are cheese, cottage cheese, ricotta and yoghurt. Dried cured sausages are an example of meat products. Examples of agricultural products are crops such as cereals, nuts, fruits, vegetables and flower bulbs. Spoilage by fungi does not only affect the quality of the product, but also represents a health risk. It is well known that some fungal species, which grow on e.g. dairy products and sausages, can produce mycotoxins. Some mycotoxins are extremely dangerous as they can cause lethal diseases. Therefore the outgrowth of unwanted fungi in and on food products should always be prevented.
Food preservation techniques, e.g. heat processing, freezing, ultrasound, irradiation, and modified atmosphere packaging, significantly reduce microbial load but of particular concern is the evidence that processed foods are being contaminated with microorganisms following processing and prior to packaging. Of rising concern in the food industry is microbial spoilage of various foods such as dairy and meat products, dressings, spreads, margarines and seafood. Especially food products in the 2.0 to 7.0 pH range are known to be susceptible to microbial spoilage by yeast, fungi, acid tolerant bacteria and/or mesophilic or thermophilic spore forming and non-spore forming bacteria.
Mostly, processed foods are not eaten directly after processing thereby permitting bacteria, yeast or mould introduced by post-contamination to grow. Since food consumption may occur without reheating the processed foods to sufficient temperatures for sufficient time, there is a risk of food poisoning or food spoilage. Furthermore, the recent trend for minimally processed foods with the intrinsic nutritional and sensory qualities of raw and fresh foods has raised a new safety risk. Milder preservation treatments, such as high hydrostatic pressure and pulsed electric fields have proved to be successful but rely on effective hurdles i.e. cold chain and addition of natural anti-microbials.
There has been extensive research conducted in the field of food safety to develop effective anti-fungal compositions. Natamycin also known as pimaricin or tennecetin, is a polyene antibiotic, which has been known since the late fifties (Struyk et al, Antibiot. Ann. 1957-1958, 878) and which is currently used as a preservative in many food and agricultural products. U.S. Pat. No. 5,821,233 discloses natamycin exhibiting a high release rate of at least 3 μg/24 hours over the first 24 hours when contacted on a carrier with an agar surface of 0.6 cm diameter, and a carrier loading of 40 μg of natamycin. U.S. Pat. No. 5,997,926 discloses natamycin complexes with similar release rates. For some food applications, this kind of natamycin with a high release rate does not offer an adequate protection because for example the duration of the protection is not sufficient and/or the stability of the natamycin is not optimal. As a consequence, higher amount of natamycin would be needed to offer an adequate protection. Natamycin with a high release rate can also penetrate too far in the product treated, which could be unwanted in some products.
To control the release of natamycin, encapsulation has been proposed, see for example WO2005/018322 and US2005/042341. Encapsulation does not change the characteristics of the natamycin itself, but it tries to ensure a slower release of natamycin by applying an extra barrier. This automatically requires extra formulation steps after the recovery of the natamycin from a natamycin source, which makes the natamycin production process more complicated then when the natamycin itself would be changed to give a slower release.
Therefore, there is still a need for improved anti-fungal compositions that could solve at least some of these problems: slower release, longer duration of protection and/or improved stability.